Trends and ethnic disparities in the incidence and outcome of stroke in Auckland, New Zealand over 20 years

Abstract

Aims: The aims of this thesis were to investigate trends and ethnic disparities in the incidence and outcome of stroke in Auckland, New Zealand between 1981 and 2003. Methods: Trends were assessed using information from the three Auckland Regional Community Stroke (ARCOS) studies, conducted in people (aged ≥15 years) in Auckland, during 12-month calendar periods in 1981-1982, 1991-1992, and 2001-2002. These studies used comparable definitions and case finding methods and have been shown to meet the stringent criteria for a population-based “ideal” stroke incidence study. Rates were calculated using Poisson distribution and are presented with 95% confidence intervals. Trends in survival were assessed using Cox Proportional hazards regression modelling. Results: Overall trends in the incidence and event rates of stroke declined across the study period. These declines were significant in males and for the ages 65 to 74 years only. However, growing disparities in the rates of stroke between the major ethnic groups in New Zealand were found, with significant declines in New Zealand Europeans and increases in Māori and Pacific populations. Dramatic improvements in survival over the study period were also found, with the greatest improvement in the acute period, within the first 28-days after stroke. Adjustments for patient or disease severity factors strengthened the survival model. However, adjustments for care/service factors nullified the survival model, thus explaining most of the improving trend. Conclusions: The small declines in the incidence of stroke, improvements in survival and the ageing of the New Zealand population will lead to data dramatic increases in the number of people living with the effects of stroke. To maintain stable numbers of strokes occurring, more intensive prevention strategies need to target high-risk populations and population-wide health education strategies are needed to improve the health of the general population, hence reducing the risk of stroke.